10 Downing Street is refusing to comment on the allegations about David Cameron and a dead pig

Britain's Prime Minister David Cameron. REUTERS/Toby Melville The UK woke up on Monday to allegations that David Cameron, the prime minister, put "a private part of his anatomy" into a dead pig's mouth as part of a university initiation ceremony.

Cameron carried out the act when he was a student at Oxford University, according to the book co-written by Lord Ashcroft and journalist Isabel Oakshott.

The prime minister's office at Number 10 Downing Street was not in the mood to comment on the bizarre story.

Journalists fresh from a briefing tweeted about it. Here's Christopher Hope, chief political correspondent at the Daily Telegraph:

It didn't even get featured in the summary of the briefing, which said: "The Prime Minister's Official Spokesperson answered questions about the Trade Union Bill, EU reform, the independence referendum and Syria."

Meanwhile, George Osborne, the Chancellor of the Exchequer, was asked about it while on a trade mission to China. He tried not to laugh and said "I haven't seen that book."

Ashcroft, a former ally, fell out with Cameron after the prime minister failed to follow through on a promise to give him a top ranking job after winning the 2010 election. The pair now infamously dislike each other.

The book, called Call Me Dave, features a source who claimed to be present during the pig incident and has photographic evidence. However, the book also makes it clear that Ashcroft and Oakshott failed to actually obtain the photo in question. That creates an obvious question of why they published this piece of gossip when they were unable to prove it, and why the Mail chose to repeat it. The Mail is usually (broadly) supportive of the Conservative Party.